Boom support structure for a hoist rope support sheave

ABSTRACT

A machine for heavy loads comprising a rope support sheave mounted on a boom between upper and lower ends of the boom for movement between a raised position wherein the sheave supports a hoist rope above the boom and a lowered position wherein the rope support sheave is accessible for maintenance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to machinery used for raising loads whichinclude a boom and supporting structure. Examples of such machinesinclude draglines and large industrial cranes.

2. Discussion of Prior Art

A walking dragline typically includes a main housing, a boom whichextends upwardly and outwardly from the main housing, and a mastassembly which extends upwardly from the main housing for supporting theboom. The boom comprises a welded frame including longitudinallyextending upper and lower pairs of chords and lacing welded between thechords. Support lines extend between the upper end of the mast assemblyand the boom for supporting the boom relative to the mast assembly. Asheave mounted for rotation about a horizontal axis is on the upper endof the boom. Hoist ropes extend from a bucket hoist mechanism, over thesheave and then to a bucket. Extending or retracting the hoist ropescauses vertical movement of the bucket. A drag rope extends from abucket drag mechanism to the bucket to permit horizontal movement of thebucket relative to the boom. The main housing is supported by a tub thatsits on the ground when the dragline is engaged in digging operations.The main housing is supported for pivotal movement relative to the tubin a lateral plane about a vertical axis. A pair of walking mechanismsare mounted on opposite sides of the main housing and are operable formoving the main housing over the ground between digging operations. Themain housing includes an operator's cab adjacent to and generallybeneath the boom. A stairway extends from the inner end to the outer endof the boom.

Because the hoisting rope or ropes are quite heavy by virtue of theirown dead weight, when these ropes become slack due to little or no loadon them, the ropes can hit the top of the boom. To prevent this fromhappening, a rope support sheave is provided partway between the lowerend and the upper end of the boom in order to prevent the hoist ropefrom hitting the boom.

When the hoisting rope is taut or under load and extends between theboom top sheave and the hoisting drum, the hoisting ropes are asubstantial distance above the boom. As a result, the rope supportsheave must be mounted a substantial distance above the boom. In theprior art, a rigid member structure was used to support the supportsheave. This added substantial weight to the boom thus reducing theamount of weight which the boom could support. The rope support sheaverequires regular maintenance due to the number of mechanical componentsinvolved with the sheave. In the prior art, additional access means suchas ladders, stairs, platforms, etc. must be added to the boom in orderto permit access to the rope support sheave for maintenance, which addsfurther weight to the boom, thus reducing the weight the boom can carry.

SUMMARY OF THE INVENTION

The invention provides a machine such as a dragline for lifting heavyloads, the machine comprising a main housing, a load hoist mechanismmounted on the housing, a boom having upper and lower ends, the lowerend being connected to the main housing and the upper end having thereona sheave mounted for rotation about a generally horizontal axis, theboom having a longitudinal axis and having two spaced apart top railsextending along the longitudinal axis, structure supporting the boomrelative to the main housing, means for lifting a load, a hoist ropeextending between the load lifting means and the load hoist mechanismand over the sheave to permit vertical movement of the load liftingmeans, a hoist rope support sheave, and means for mounting the ropesupport sheave on the top of the boom partway between the lower andupper ends of the boom, the mounting means comprising a first sheavesupport link pivotally connected to one of the boom rails and a secondsheave support link pivotally connected to the other of the boom rails,the first and second sheave support links extending from the boom in anupright support position and having upper ends, a cross pin extendingbetween the upper ends of the sheave support links, the hoist ropesupport sheave being rotatably mounted on the cross pin, and means formaintaining the support links in their upright support position and forpivoting the support links between their upright supporting position anda lowered maintenance position.

One of the primary features of the invention is to increase the amountof load a boom can carry by providing a lightweight sheave supportstructure.

It is another of the principal advantages of the invention to provide arope support sheave which can be pivoted downwardly to limit the needfor extra access structure to permit maintenance of the rope supportsheave. This further reduces the extra weight added to the boom andincreases its load carrying capabilities.

It is another of the principal advantages of the invention to provide arope support sheave structure which is one-third to one-half the weightof the prior art structure but at comparable cost.

Other features and advantages of the invention will become apparent tothose skilled in the art upon review of the following detaileddescription, claims and drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a dragline embodying the invention.

FIG. 2 is a top plan view of a rope support sheave structure on theboom.

FIG. 3 is a side elevational view of the rope support sheave structureon the boom.

Before one embodiment of the invention is explained in detail, it is tobe understood that the invention is not limited in its application tothe details of the construction and the arrangements of components setforth in the following description or illustrated in the drawings. Theinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. Also, it is to be understood that thephraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. Use of "including"and "comprising" and variations thereof as used herein is meant toencompass the items listed thereafter and equivalents thereof, as wellas additional items. Use of "consisting of" and variations thereof asused herein is meant to encompass only the items listed thereafter andequivalents thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention is directed to a machine for lifting heavy loads. One suchmachine is an industrial crane. In this embodiment, a walking dragline10 embodying the invention is illustrated in the drawings. The dragline10 comprises (see FIG. 1) a main housing 12. The dragline 10 alsocomprises a bucket hoist mechanism 20 and a bucket drag mechanism 22,both of which are mounted on the main housing 12. A boom 24 extendsupwardly and outwardly from the main housing 12. The upper end of theboom 24 has thereon a sheave 26 which is rotatable about a horizontalaxis. A hoist rope 28 extends between the bucket hoist mechanism 20 andover the sheave 26 to means for engaging or lifting a load, such as abucket 29, to permit vertical movement of the bucket 29 relative to theboom 24. A drag rope 31 extends from the bucket drag mechanism 22 to thebucket 29 to permit horizontal movement of the bucket 29.

The boom 24 is supported relative to the main housing 12 by aconventional mast assembly 32. Support lines 33 are connected betweenthe upper end of the mast assembly 32 and the boom 24 for supporting theboom 24 relative to the mast assembly 28. When the dragline 10 isdigging, the main housing 12 is supported by a tub 31 that sits on theground. The main housing 12 is supported for pivotal movement relativeto the tub 31 in a lateral plane about a vertical axis. A pair ofwalking mechanisms 34 (one shown) move the main housing 12 over theground between digging operations. The main housing 12 includes anoperator's cab 35 adjacent to and generally below the boom 24. Thedragline 10 as thus far described is conventional.

Referring to FIG. 1, the boom 24 includes a lower section 36, an uppersection 37, and a center section 38 intermediate the lower and uppersections 36 and 37. In the illustrated embodiment, the boom 24 isrectangular in cross-section.

Because the hoisting rope or ropes 28 are quite heavy by virtue of theirown dead weight, when these ropes become slack due to little or no loadon them, the ropes 28 can hit the top section 37 of the boom 24. Toprevent this from happening, a rope support sheave 39 is providedpartway between the lower end and the upper end of the boom 24 in orderto prevent the hoist rope 28 from hitting the boom 24. When the hoistingrope 28 is taut or under load and extends between the boom top sheave 26and the hoisting drum 20, the hoisting rope 28 is a substantial distanceabove the boom 24. As a result, the rope support sheave 39 must bemounted a substantial distance above the boom 24.

Referring now to FIG. 2, the top of the boom 24 is formed from twoparallel spaced apart chords or rails 40 and 42. The dragline 10 furtherincludes means for mounting the rope support sheave 39 on the top of theboom 24, the mounting means or structure 44 comprising a first supportlink 46 pivotally connected to one rail 40 and a corresponding secondsupport link 50 pivoted to the other boom rail 42. Extending between theupper ends of the support links is a cross pin 54. The rope supportsheave 39 is slidably mounted upon the cross pin 54 and is free torotate about the pin 54. Thus, when the hoist rope 28 is trained overthe sheave 39, the sheave 39 can rotate as the rope 28 moves over thesheave 39 and, as the hoist rope 28 moves from left to right in FIG. 2as it is paid out from the hoist drum 20, the sheave 39 can move backand forth along the cross pin 54 to limit the fleet angle of the hoistrope 28. In other embodiments, more than one rope support sheave 39 onthe cross pin 54, as well as additional hoist ropes 28, can be used.

The sheave mounting structure 44 also includes means for maintaining thesupport links in their upright position and for pivoting the supportlinks between their upright supporting position and a loweredmaintenance position. The pivoting means comprises a first pivot rope 60which extends between the upper end of the first support link 46 and thesecond boom rail 42 and a second pivot rope 64 attached to the othersupport link 50 and the first boom rail 40. In other embodiments (notshown), the pivot ropes 60 and 64 could be connected between the linkand the rail which supports the support link.

Each of the pivot ropes 60 and 64 is a fixed length between each of itsrespective support links and its boom rail and is flexible. Accordingly,when the support links 46 and 50 are pivoted from their upright positionto their lowered maintenance position, the pivot ropes 60 and 64 flexand move out of the way. As the support links 46 and 50 are pivoted backto their upright position, clockwise as shown in FIG. 3, movement of thesupport links is limited by the ropes 60 and 64, and the ultimateposition of the support links is determined by the fixed length of thepivot ropes 60 and 64.

The pivoting means further includes a first support rope 70 for holdingthe first support link 46 in its upright vertical position and forlowering the support link 46 to its maintenance position. The firstsupport rope 70 is attached to the upper end of the support link 46 andat its other end to a first winch 74 mounted on the first boom rail 40.The winch 74 can pay out the support rope 70 in order to lower the ropesupport sheave 39 to its maintenance position (shown in ghost in FIG. 3)or the winch 74 can rotate in the other direction to raise the supportlink 46 and rope support sheave 39 to its vertical support position. Asecond support rope 78 (shown only in FIG. 2 because it is behind therope 70 in FIG. 3) and a second winch 82 (behind winch 74 in FIG. 3) areprovided in a comparable fashion for the second support link 50 on thesecond boom rail. Winches 74 and 82 operate together. In otherembodiments, other support rope arrangements can be used. For example, asingle support rope on a rail (not shown) extending across the boomrails could also be used.

In the preferred embodiment, the pivoting means further includes a firstpivot link 88 fixed at one end to the support rope 70 and pivotallymounted at its other end to the boom rail 40 at the lower end of thesupport link 46. A comparable second pivot link 92 (shown only in FIG.2) is also mounted on the other boom rail 42. The pivot links aid in theraising and lowering of the support links. In other embodiments, thepivot links can be omitted. Each of the links and ropes is pivotallymounted to its respective support rail by spaced apart lugs 94 and a pin96 which extends between the lugs and through openings in the respectivelink or rope member.

In operation, a maintenance operator will operate the winches 74 and 82in order to pay out the support ropes and lower the rope support sheave39 to a platform 98 which extends between the spaced apart boom rails 40and 42. With the sheave 39 at the platform 98, maintenance on the sheavecan be undertaken.

High strength structural strand or wire rope can be used for both thepivot ropes and the support ropes. The combination of the use ofstructural strand or wire rope and less maintenance structure reducesthe weight of the support sheave structure by one-third to one-half ofthe prior art weight, while keeping the cost of the sheave supportstructure about the same.

Various features of the invention are set forth in the following claims.

I claim:
 1. A machine for lifting heavy loads, the machine comprisingamain housing, a load hoist mechanism mounted on said housing, a boomhaving upper and lower ends, said lower end being connected to said mainhousing and said upper end having thereon a sheave mounted for rotationabout a generally horizontal axis, said boom having a longitudinal axisand having a first boom top rail and a second boom top rail spaced apartfrom said first boom rail, both rails extending along said longitudinalaxis, structure supporting said boom relative to said main housing,means for lifting a load, a hoist rope extending between said loadlifting means and said load hoist mechanism and over said sheave topermit vertical movement of said load lifting means, a hoist ropesupport sheave, and means for mounting said rope support sheave on thetop of said boom partway between the lower and upper ends of said boom,said mounting means comprisinga first sheave support link pivotallyconnected to said first boom rail, a second sheave support linkpivotally connected to said second boom rail, said first and secondsheave support links extending from said boom in an upright supportposition and having upper ends, a cross pin extending between the upperends of said sheave support links, said hoist rope support sheave beingrotatably mounted on said cross pin, and means for maintaining saidsupport links in their upright support position and for pivoting saidsupport links between their upright supporting position and a loweredmaintenance position.
 2. A machine according to claim 1 wherein saidmeans for maintaining the support links in their upright position andfor pivoting the support links between their upright supporting positionand a lowered maintenance position comprises a first pivot rope which isattached to the upper end of said first support link and to one of theboom rails and a second pivot rope which is attached to the upper end ofsaid second support link and to the other of said boom rails.
 3. Amachine according to claim 2 wherein said first pivot rope is attachedto the second boom rail and said second pivot rope is attached to saidfirst boom rail.
 4. A machine according to claim 2 wherein said firstand second pivot ropes are a fixed length between each of its respectivesupport links and its boom rail and are flexible.
 5. A machine accordingto claim 2 wherein said pivoting means further includes a first supportrope for holding the first support link in its upright vertical positionand for lowering the support link to its maintenance position, saidfirst support rope being attached at one end to the upper end of thefirst support link and at its other end to a first winch mounted on thefirst boom rail.
 6. A machine according to claim 5 wherein said pivotingmeans further includes a second support rope for holding the secondsupport link in its upright vertical position and for lowering thesecond support link to its maintenance position, said second supportrope being attached at one end to the upper end of the second supportlink and at its other end to a second winch mounted on the second boomrail.
 7. A machine according to claim 6 wherein said pivoting meansfurther includes a first pivot link fixed at one end to the firstsupport rope and pivotally mounted at its other end to the first boomrail and a second pivot link fixed at one end to the second support ropeand pivotally mounted at its other end to the second boom rail.
 8. Amachine according to claim 1 wherein said machine further includes aplatform which extends between the spaced apart boom rails.
 9. Adragline comprisinga main housing, a bucket hoist mechanism mounted onsaid housing, a bucket drag mechanism mounted on said main housing, amoving mechanism for moving said main housing over the ground, a boomhaving upper and lower ends and a rectangular cross-section, said lowerend being connected to said main housing, said upper end having thereona sheave, said boom having a longitudinal axis, said sheave beingmounted for rotation about a generally horizontal upper axis, said boomhaving a first boom top rail and a second boom top rail spaced apartfrom said first boom rail, both rails extending along said longitudinalaxis, structure supporting said boom relative to said main housing,means for lifting a load, a hoist rope extending between said loadlifting means and said load hoist mechanism and over said sheave topermit vertical movement of said load lifting means, a hoist ropesupport sheave, and means for mounting said rope support sheave on thetop of said boom partway between the lower and upper ends of said boom,said mounting means comprisinga first sheave support link pivotallyconnected to said first boom rail, a second sheave support linkpivotally connected to said second boom rail, said first and secondsheave support links extending from said boom in an upright supportposition and having upper ends, a cross pin extending between the upperends of said sheave support links, said hoist rope support sheave beingrotatably mounted on said cross pin, and means for maintaining saidsupport links in their upright support position and for pivoting saidsupport links between their upright supporting position and a loweredmaintenance position.
 10. A dragline according to claim 9 wherein saidmeans for maintaining the support links in their upright position andfor pivoting the support links between their upright supporting positionand a lowered maintenance position comprises a first pivot rope which isattached to the upper end of said first support link and to one of theboom rails and a second pivot rope which is attached to the upper end ofsaid second support link and to the other of said boom rails.
 11. Adragline according to claim 10 wherein said first pivot rope is attachedto the opposite second boom rail and said second pivot rope is attachedto said first boom rail.
 12. A dragline according to claim 10 whereinsaid first and second pivot ropes are a fixed length between each of itsrespective support links and its boom rail and are flexible.
 13. Adragline according to claim 10 wherein said pivoting means furtherincludes a first support rope for holding the first support link in itsupright vertical position and for lowering the support link to itsmaintenance position, said first support rope being attached at one endto the upper end of the first support link and at its other end to afirst winch mounted on the first boom rail.
 14. A dragline according toclaim 13 wherein said pivoting means further includes a second supportrope for holding the second support link in its upright verticalposition and for lowering the second support link to its maintenanceposition, said second support rope being attached at one end to theupper end of the second support link and at its other end to a secondwinch mounted on the second boom rail.
 15. A dragline according to claim14 wherein said mounting means further includes a first pivot link fixedat one end to the first support rope and pivotally mounted at its otherend to the first boom rail and a second pivot link fixed at one end tothe second support rope and pivotally mounted at its other end to thesecond boom rail.
 16. A dragline according to claim 9 wherein saiddragline further includes a platform which extends between the spacedapart boom rails.
 17. A machine for lifting heavy loads, the machinecomprisinga main housing, a load hoist mechanism mounted on saidhousing, a boom having upper and lower ends, said lower end beingconnected to said main housing and said upper end having thereon asheave mounted for rotation about a horizontal axis, structuresupporting said boom relative to said main housing, means for engaging aload, a hoist rope extending between said load engaging means and saidload hoist mechanism and over said sheave to permit vertical movement ofsaid load engaging means, and a rope support sheave mounted on said boombetween said upper and lower ends of said boom for movement between araised position wherein said sheave supports said hoist rope above saidboom and a lowered position wherein said rope support sheave isaccessible for maintenance.
 18. A machine as set forth in claim 17 andfurther comprising a link mounted on said boom for pivotal movementrelative thereto between raised and lowered positions corresponding tosaid raised and lowered positions of said rope support sheave, andwherein said rope support sheave is pivotally mounted on said link. 19.A machine as set forth in claim 17 and further comprising first andsecond links mounted on said boom for pivotal movement relative theretobetween respective raised and lowered positions corresponding to saidraised and lowered positions of said rope support sheave, and a crosspin extending between said first and second links, and wherein said ropesupport sheave is pivotally mounted on said cross pin.
 20. A machine asset forth in claim 19 and further comprising means for selectivelymoving said links between said raised and lowered positions and forselectively maintaining said links in said raised positions.